Multi-break fabric



United States Patent O 3,256,130 MULTI-BREAK FABRIC .lohn L. Nisbet andHubert C. Woodall, Jr., Winston- Salem, N.C., assignors to CarolinaInsulatiug Yarn Company, Winston-Salem, N.C., a corporation of NorthCarolina Filed Aug. 3, 1961, Ser. No. 129,081 2 Claims. (Cl. 161-89) Thepresent invention relates to a system of lfibers having controlledstrength and stretch characteristics. More specifically the presentinvention provides an arrangement of fibers such as glass fibers whichare disposed in a predetermined pattern so as to constitute a mat orfabric having a predictable stretch and strength characteristic in allor in predetermined directions.

It is well known that many fibers, both organic and inorganic havecharacteristics which make such fibers desirable for incorporation' asreinforcement in impregnated or laminated materials. Metal fibers, forexample, have high strength but low elasticity characteristics. Thepresent invention provides a fabric and method of forming an elasticmaterial using nonelastic reinforcement. While glass fibers are used inthe specific example given herein it will be recognized that otherfibers possess similar characteristics and could be used in like manner.

Glass fibers have many desirable characteristics for certain purposes.They possess good electrical insulating properties, high strength toweight ratio, high thermal resistivity and are resistant to oils, acidsand corrosive atmospheres. Glass fibers do not, however, possess anyappreciable elasticity and hence, fabric woven from such fibers will notstretch in order to conform to shapes having, for example, doublecurvatures. This characteristic presents a problem when fabrics are madeup of woven glass fiber inmpregnated with rubber or any other material.strong and possess good electrical insulating characteristics but don-ot conform to shapes having curvatures requiring stretchability.

It is also desirable to provide a material in the form of a mat orfabric providing a multi-break material which will give or -breakcertain fibers on initial tension and will maintain its continuitythrough the medium of a second set of fibers until a predeterminedpercent of elongation is reachedwhereupon a third set of fibers isrelied upon for strength and continuity. In this manner material may befabricated having predictable stretch characteristics in which aninitial impact will cause the material to give by breaking a certain setof fibers but in which the impact will be contained by ahigh strength,controlled elasticity final set of fibers. Additional sets of fibers maybe provided if desired.

Materials have :been designed heretofore utilizing woven glass fiberimpregnated with rubber or other suitable compound. In order to givesuch materials some degree of stretchability the glass fiber-fabric isinserted on the bias. This type of material has a degree of flexibilitybut the fabric usually must be spliced along its length because of thebias fabric, also the width of the fabric decreases -appreciably whenthe material is elongated.

According to the present invention there is provided a mat or fabriccomprising a first system of glass fiber yarns which are arranged in acurved pattern with a second system of warp yarns knitted to retain theglass fiber yarns in their predetermined pattern Within the mat orfabric. The third warp yarn system may be of a different materialcontaining less geometric extensibility and different strengthcharacteristics than the fibers used in the first system. The elongationof the fabric can be controlled during impregnation or coating and whenSuch fabrics, if not biased, are unusuallyY is shown in FIG. 1.

3,256,130 Patented June 14, 1966 the material must be stretched toconform to a desired shape certain of the warp yarns will break topermit the material to assume the desired configuration. The ultimatestrength of the material is not adversely affected by this breaking ofcertain warp yarns since the glass fibers forming the first system andconstituting the principal strength of the reinforcement are still'present in continuous form. Furthermore, the warp yarns, while brokenand not continuous over great lengths of the fabric, are present and doadd to the overall strength of a coated or impregnated material. Thus,the present invention provides a means whereby the desirablecharacteristics of glass fibers may be incorporated in a material havingthe additional desirable characteristic of stretchability at the desiredtime.

The present invention finds application as a laminating media where itis desirable that the fabric give slightly under an initial impact butthat the ultimate strength of the material be high to preventpenetration by the impacting object. The formability of the inventionlends itself to products having double curvatures.

A11 object of the present invention is to provide a fabric or mat havingmultiple break characteristics.

Another object of the present invention is to provide a fabric or mathaving a plurality of systems of fibers including glass bers, thevarious systems of fibers having varying strength and elasticcharacteristics so that one set `of fibers yields under a predeterminedtension Without adversely affecting the ultimate strength of thematerial.

Still Vanother object of the present invention is to provide aninsulating material having .a plurality of systems of fibers impregnatedor coated therein, including glass fibers, the material beingstretchable by virtue of breaking one or more sets of fibers, the glassfibers forming the ultimate strength of the reinforcement remaining incontinuous form.

Other objects and many of the attendant advantages of the presentinvention will becomemore fully apparent upon consideration of thefollowing detailed specification in -connection with the accompanyingdrawings wherein:

FIG. 1 is a plan view of one embodiment of a fabric according to thepresent invention and,

FIG. 2 is a knitting diagram of the fabric shown in FIG. 1.

The present invention comprises a plurality of individual systems offibers which are arranged in a predetermined pattern so as to constitutea mat of set pattern and having controlled strength and elongationcharacteristics.

A fabric according to one embodiment of the invention, It can be seenthat this fabric is composed of warp yarns 1 and 2 which form a supportfor the sinusoidally curved yarns 3.

yThe particular fabric shown is made on a warp knitting machine and theknitting diagram for -this particular fabric is shown in FIG. 2. It canbe seen that the yarn 1 is knitted, being wrapped around the needlesalternately in opposite directions. The yarn 2 is passed on either sideof the needle in each course. The yarn 3 is laid in the warp yarns andis shifted laterally in each course in alternate directions so as tohave a sinusoidal form as shown. In the particular example disclosed theyarn 1 is 40 denier polyester, the yarn 3 is /2/ 2 glass fiber and theyarn 2 is 900/1/2 glass fiber. The fabric disclosed in FIG. l may beimpregnated with a material such as a silicone rubber when used as atape. Since the fibers are of a controlled thickness and the pattern offibers is generally uniform throughout the length of the fabric, thetape'will be of uniform thickness throughout. When such a material iswrapped around an irregularly shaped object, the yarn 2 will initiallybreak for the reason that, in the particular fabric disclosed, thesefibers are glass and in this design have a straighter configurationwhereas the fibers 1 are of polyester and possess greater elasticity.Thus, the yarns 2 comprise a first system of bers which break to givethe reinforced material a degree of elasticity. If greater extensibilityis required than is derived from a breaking7 of the yarns 2, the yarns 1of polyester may also break and the reinforced tape may be stretcheduntil the fibers 3 are extending substantially longitudinally of thetape. The strength characteristics of the impregnated material are notadversely affected by the breaking of the warp yarns since these yarnsare still in the tape and the ultimate strength of the tape is based onthe presence of the glass fibers 3.

It should be recognized that the specific pattern of the fabric may bevaried to suit'varying operational requirements. It is possible toutilize yarns of different size and materials in place of the yarns 1and 2. The glass fiber yarns 3 may be arranged in any suitable patternand it is only necessary that these yarns be supported by the knittedwarp yarns and be disposed in a pattern to give the resulting fabric thedesired ultimate strength and extensibility characteristics.

It will be noted that none of the yarns in this disclosed embodimentextend across the entire width of the material. This prevents wickingoccurring across the width of any fabric so constructed and where slitor coated it does not destroy the integrity of the material.

it is also possible to construct a fabric in accordance with the presentinvention wherein the yarns used to retain the ultimate strength fibersin place during manufacture of the impregnated material may besubsequently removed from the material. That is to say, the yarns 1 and2 which retain the yarns 3 in a predetermined pattern may be made of amaterial which by subsequent chemical treatment will be dissolved sothat the fabricated material will contain only the yarns 3. It is alsowithin the realm of the present invention to thermally fuse the warpyarn after the material is impregnated so as to provide a materialhaving substantial elasticity and possessing the strengthcharacteristics of tape reinforced with glass fiber.

It is also possible according to the present invention to break theyarns 2 by passing the impregnated tape between a pair of differentialrollers, the second pair being driven at a greater speed than the firstpair so that the tape is tensioned therebetween. This controlled tensionwill break the yarns 2 and give the tape the desired degree ofelasticity.

It can be seen that the present invention provides a fabric in thenature of a mat wherein the strength and elongation characteristics arecontrolled and readily predictable. According to this general embodimentone or more systems of warp yarns are used to retain one or moresinusoidally or otherwise disposed systems of glass fibers in place andthese retaining systems break under tension, thereby providing thematerial with a certain elasticity and the ability to conform to shapesrequiring stretch in more than one direction. The remaining unbrokenyarns provide the ultimate strength of the material and these yarns aremaintained in continuous form up to the ultimate strength points of thematerial.

Obviously many modifications and variations of the present invention arepossible in light of the above teachings.

What is claimed as new and desired to be secured by Letters Patent is:

1. An impregnated material having at least three systems of fibrousmaterial, a first set of nonelastic high strength fibers forming a firstset of yarns running warpwise of the fabric, a second set of elasticrelatively low strength fibers forming a second set of yarns knitted inseparate courses, a third set of nonelastic high strength fibers forminga third set of yarns extending in a zigzag pattern warpwise of thefabric, said second set of yarns knitted to retain said first and thirdsets of yarns and said first set of yarns maintaining said third set ofyarns in said zigzag pattern, said first set of yarns of the impregnatedmaterial adapted to be disrupted so as to permit the impregnatedmaterial to stretch to the length of the third set of yarns.

2. A tape comprising an impregnated fabric, the fabric including a firstset of yarns extending warpwise of the fabric, said first set of yarnscomprising nonelastic high strength glass fibers, a second set of yarnsknitted in separate courses, said second set of yarns comprisingrelatively elastic low strength synthetic fibers, and a third set ofyarns extending in a zig-zag pattern through the separate knittedcourses of the second set of yarns, said third set of yarns comprisingnon-elastic high strength glass fibers, said first set of yarns adaptedto be disrupted so that said tape is extensible to the elastic limit ofthe second set of yarns, said second set of yarns adapted to bedisrupted so that the tape is extensible to the full length of thezig-zag third set of yarns.

References Cited by the Examiner UNITED STATES PATENTS 2,142,908 1/1939Mendel 66-193 2,539,301 1/1951 Foster 28-72 2,587,117 2/1952 Clay 23-72,831,235 4/1958 Taylor 28--7-1r 2,879,581 3/1959 Evans et al. 28-802,913,801 11/1959 Kessler et al. 28-74 2,956,331 10/1960 Whitehead 28-802,967,415 1/1961 Ford et al 66-193 3,106,079 10/1963 Kohl 66-1933,127,306 3/1964 Turton et al 66-202 X FOREIGN PATENTS 273,935 8/1951Switzerland.

ROBERT R. MACKEY, Acting Prima/'y Examiner.

RUSSELL C. MADER, DONALD W. PARKER,

Exam rlers.

H. G. GARNER, P. C. FAW, Assistant Examiners.

1. AN IMPREGNATED MATERIAL HAVING AT LEAST THREE SYSTEMS OF FIBROUS MATERIAL, A FIRST SET OF NONELASTIC HIGH STRENGTH FIBERS FORMING A FIRST SET OF YARNS RUNNING WARPWISE OF THE FABRIC, A SECOND SET OF ELASTIC RELATIVELY LOW STRENGTH FIBERS FORMING A SECOND SET OF YARNS KNITTED IN SEPARATE COURSES, A THIRD SET OF NONELASTIV HIGH STRENGTH FIBERS FORMING A THIRD SET OF YARNS EXTENDINF IN A ZIGZAG PATTERN WARPWISE OF THE FABRIC, SAID SECOND SET OF YARNS KNITTED TO RETAIN SAID FIRST AND THIRD SETS OF YARNS AND SAID FIRST SET OF YARNS MAINTAINING SAID THIRD SET OF YARNS IN SAID ZIGZAG PATTERN, SAID FIRST SET OF YARNS OF THE IMPREGNATED MATERIAL ADAPTED TO BE DISRUPTED SO AS TO PER- 